US4610515AExpiredUtility
Objective lens for an optical disc
Est. expiryMar 26, 2003(expired)· nominal 20-yr term from priority
Inventors:Masashi Tanaka
G11B 2007/13727G11B 7/1374G02B 13/24G02B 13/00
84
PatentIndex Score
26
Cited by
6
References
8
Claims
Abstract
An objective lens for recording information on an optical disc at high density or reproducing it comprises, in succession from the farther conjugate point side of the objective lens toward the nearer conjugate point side, first lens member consisting of a negative lens whose concave surface is directed toward the farther conjugate point side and a positive lens cemented together, second lens member of a positive lens and third lens member of a positive meniscus lens whose convex surface is directed toward the farther conjugate point side. A numerical aperture of the objective lens is 0.45 to 0.6 and the working distance thereof is long.
Claims
exact text as granted — not AI-modifiedI claim:
1. An objective lens for recording or reproducing information on a optical disc at high density comprising, in succession from the farther conjugate point side of the objective lens toward the nearer conjugate point side thereof; a first lens member consisting of a negative lens whose concave surface is directed toward the farther conjugate point side and a positive lens cemented together, a second lens member consisting of a positive lens, and a third lens member consisting of a positive meniscus lens whose convex surface is directed toward the farther conjugate point side, and said objective lens satisfying the following conditions: d3/f<1.0 0.12<n2 -n1 -0.02<f/f.sub.1 <0.07 0.7<f.sub.2 /f.sub.3 <1.5 0.6<r.sub.1 /f<1.5 wherein d3 represents air spacing between the first and second lens members; f represents focal distance of the entire system; n1 and n2 represent refractive indicas of the negative lens and the positive lens in the first lens member for the wavelength in use; f 1 , f 2 and f 3 represent focal distances of the first, second and third lens members, respectively; and r 1 represents radius of curvature of the foremost lens surface of the first lens member whose concave surface is directed toward the farther conjugate point side.
2. An objective lens according to claim 1, having the numerical data substantially as set forth in the following table. ______________________________________
f = 1.0 N.A. = 0.55
s = 0.04076 t = 0.4027
______________________________________
r.sub.1 = -1.3504
d.sub.1 = 0.2013
n.sub.1 = 1.49434
G.sub.1
r.sub.2 = 11.6239
d.sub.2 = 0.3758
n.sub.2 = 1.78151
r.sub.3 = -2.5831
d.sub.3 = 0.4161
r.sub.4 = 1.9454
d.sub.4 = 0.3221
n.sub.3 = 1.78151
G.sub.2
r.sub.5 = 84.6826
d.sub.5 = 0.0268
r.sub.6 = 0.8590
d.sub.6 = 0.4564
n.sub.4 = 1.78151
G.sub.3
r.sub.7 = 1.4067
f.sub.1 = -1029.03
f.sub.2 = 2.54
f.sub.3 = 2.07
______________________________________
wherein r 1 , r 2 , r 3 , . . . represent radii of curvature of individual lens surfaces in succession from the farther conjugate point side; d 1 , d 2 , d 3 , . . . represent center thicknesses of individual lenses and spacings between lenses; n 1 , n 2 , n 3 . . . represent refractive indexes of individual lenses for wavelength of 830 nm; f 1 , f 2 , f 3 represent the focal distance of the first, second and third lens members, respectively; f represents focal distance of the entire system; s represents a distance from final lens surface r 7 to a cover glass D; and t represents a thickness of the cover glass D.
3. An objective lens according to claim 1, having the numerical data substantially as set forth in the following table. ______________________________________
f = 1.0 N.A. = 0.5
s = 0.4968 t = 0.3333
______________________________________
r.sub.1 = -1.2711
d.sub.1 = 0.1667
n.sub.1 = 1.49434
G.sub.1
r.sub.2 = 10.4394
d.sub.2 = 0.3111
n.sub.2 = 1.78151
r.sub.3 = -2.3316
d.sub.3 = 0.1829
r.sub.4 = 1.8579
d.sub.4 = 0.2667
n.sub.3 = 1.78151
G.sub.2
r.sub.5 = 49.8160
d.sub.5 = 0.0222
r.sub.6 = 0.8201
d.sub.6 = 0.3778
n.sub.4 = 1.78151
G.sub.3
r.sub.7 = 1.2952
f.sub.1 = 94.38
f.sub.2 = 2.46
f.sub.3 = 2.12
______________________________________
wherein r 1 , r 2 , r 3 , . . . represent radii of curvature of individual lens surfaces in succession from the farther conjugate point side; d 1 , d 2 , d 3 , . . . represent center thicknesses of individual lenses and spacings between lenses; n 1 , n 2 , . . . represent refractive indexes of individual lenses for wavelength of 830 nm; f 1 , f 2 , f 3 represent the focal distance of the first, second and third lens members, respectively; f represents focal distance of the entire system; s represents a distance from final lens surface r 7 to a cover glass D; and t represents a thickness of the cover glass D.
4. An objective lens according to claim 1, having the numerical data substantially as set forth in the following table. ______________________________________
f = 1.0 N.A. = 0.55
s = 0.4100 t = 0.4021
______________________________________
r.sub.1 = -1.2476
d.sub.1 = 0.2011
n.sub.1 = 1.64269
G.sub.1
r.sub.2 = 7.3915
d.sub.2 = 0.3753
n.sub.2 = 1.78151
r.sub.3 = -1.8224
d.sub.3 = 0.4156
r.sub.4 = 1.8518
d.sub.4 = 0.3217
n.sub.3 = 1.78151
G.sub.2
r.sub.5 = 114.1643
d.sub.5 = 0.0268
r.sub.6 = 0.8206
d.sub.6 = 0.4558
n.sub.4 = 1.78151
G.sub.3
r.sub.7 = 1.0568
f.sub.1 = 183.89
f.sub.2 = 2.41
f.sub.3 = 2.54
______________________________________
wherein r 1 , r 2 , r 3 , . . . represent radii of curvature of individual lens surfaces in succession from the farther conjugate point side; d 1 , d 2 , d 3 , . . . represent center thicknesses of individual lens and spacings between lenses; n 1 , n 2 , . . . represent refractive indexes of individual lenses for wavelength of 830 nm; f 1 , f 2 , f 3 represent the focal distance of the first, second and third lens members, respectively; f represents focal distance of the entire system; s represents a distance from final lens surface r 7 to a cover glass D; and t represents a thickness of the cover glass D.
5. An objective lens according to claim 1, having the numerical data substantially as set forth in the following table. ______________________________________
f = 1.0 N.A. = 0.6
s = 0.6189 t = 0.4000
______________________________________
r.sub.1 = -1.0641
d.sub.1 = 0.8000
n.sub.1 = 1.49435
G.sub.1
r.sub.2 = -102.6990
d.sub.2 = 0.4800
n.sub.2 = 1.78151
r.sub.3 = -2.1606
d.sub.3 = 0.5333
r.sub.4 = 2.4466
d.sub.4 = 0.3733
n.sub.3 = 1.78151
G.sub.2
r.sub.5 = -36.5010
d.sub.5 = 0.0267
r.sub.6 = 1.0019
d.sub.6 = 0.4533
n.sub.4 = 1.78151
G.sub.3
r.sub.7 = 1.4431
f.sub.1 = 34.22
f.sub.2 = 2.95
f.sub.3 = 2.85
______________________________________
wherein r 1 , r 2 , r 3 , represent radii of curvature of individual lens surfaces in succession from the farther conjugate point side; d 1 , d 2 , d 3 , . . . represent center thicknesses of individual lenses and spacings between lenses; n 1 , n 2 , . . . represent refractive indexes of individual lenses for wavelength of 830 nm; f 1 , f 2 , f 3 represent the focal distance of the first, second and third lens members, respectively; f represents focal distance of the entire system; s represents a distance from final lens surface r 7 to a cover glass D; and t represents a thickness of the cover glass D.
6. An objective lens according to claim 1, having the numerical data substantially as set forth in the following table. ______________________________________
f = 1.0 N.A. = 0.55
s = 0.53685 t = 0.3423
______________________________________
r.sub.1 = -1.1410
d.sub.1 = 0.1997
n.sub.1 = 1.51024
G.sub.1
r.sub.2 = 4.4705
d.sub.2 = 0.3423
n.sub.2 = 1.78151
r.sub.3 = -2.0367
d.sub.3 = 0.0285
r.sub.4 = 1.6987
d.sub.4 = 0.2853
n.sub.3 = 1.78151
G.sub.2
r.sub.5 = 12.8603
d.sub.5 = 0.0285
r.sub.6 = 0.8281
d.sub.6 = 0.3138
n.sub.4 = 1.78151
G.sub.3
r.sub.7 = 1.2551
f.sub.1 = 19.34
f.sub.2 = 2.48
f.sub.3 = 2.36
______________________________________
wherein r 1 , r 2 , r 3 , . . . represent radii of curvature of individual lens surfaces in succession from the farther conjugate point side; d 1 , d 2 , d 3 , . . . represent center thicknesses of individual lenses and spacings between lenses; n 1 , n 2 , . . . represent refractive indexes of individual lenses for wavelength of 830 nm; f 1 , f 2 , f 3 represent the focal distance of the first, second and third lens members, respectively; f represents focal distance of the entire system; s represents a distance from final lens surface r 7 to a cover glass D; and t represents a thickness of the cover glass D.
7. An objective lens according to claim 1, having the numerical data substantially as set forth in the following table. ______________________________________
f = 1.0 N.A. = 0.47
s = 0.7755 t = 0.0756
______________________________________
r.sub.1 = -0.83367
d.sub.1 = 0.1763
n.sub.1 = 1.51024
G.sub.1
r.sub.2 = -9.5244
d.sub.2 = 0.3022
n.sub.2 = 1.78151
r.sub.3 = -1.3876
d.sub.3 = 0.0252
r.sub.4 = 2.0184
d.sub.4 = 0.2771
n.sub.3 = 1.78151
G.sub.2
r.sub.5 = -13.52442
d.sub.5 = 0.0252
r.sub.6 = 0.8332
d.sub.6 = 0.3022
n.sub.4 = 1.78151
G.sub.3
r.sub.7 = 1.1384
f.sub.1 = 44.90
f.sub.2 = 2.27
f.sub.3 = 2.77
______________________________________
wherein r 1 , r 2 , r 3 , . . . represent radii of curvature of individual lens surfaces in succession from the farther conjugate point side; d 1 , d 2 , d 3 , . . . represent center thicknesses of individual lenses and spacings between lenses; n 1 , n 2 , . . . represent refractive indexes of individual lenses for wavelength of 830 nm; f 1 , f 2 , f 3 represent the focal distance of the first, second and third lens members, respectively; f represents focal distance of the entire system; s represents a distance from final lens surface r 7 to a cover glass D; and t represents a thickness of the cover glass D.
8. An objective lens according to claim 1, having the numerical data substantially as set forth in the following table. ______________________________________
f = 1.0 N.A. = 0.55
s = 0.4210 t = 0.3217
______________________________________
r.sub.1 = -1.3486
d.sub.1 = 0.2011
n.sub.1 = 1.57074
G.sub.1
r.sub.2 = 32.4115
d.sub.2 = 0.3753
n.sub.2 = 1.78151
r.sub.3 = -2.0382
d.sub.3 = 0.7507
r.sub.4 = 1.7826
d.sub.4 = 0.3217
n.sub.3 = 1.78151
G.sub.2
r.sub.5 = 21.0971
d.sub.5 = 0.0268
r.sub.6 = 0.7768
d.sub.6 = 0.4558
n.sub.4 = 1.78151
G.sub.3
r.sub.7 = 0.9873
f.sub.1 = 46.54
f.sub.2 = 2.47
f.sub.3 = 2.39
______________________________________
wherein r 1 , r 2 , r 3 , . . . represent radii of curvature of individual lens surfaces in succession from the farther conjugate point side; d 1 , d 2 , d 3 , . . . represent center thicknesses of individual lenses and spacings between lenses; n 1 , n 2 , . . . represent refractive indexes of individual lenses for wavelength of 830 nm; f 1 , f 2 , f 3 represent the focal distance of the first, second and third lens members, respectively; f represents focal distance of the entire system; s represents a distance from final lens surface r 7 to a cover glass D; and t represents a thickness of the cover glass D.Cited by (0)
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